It is an object of the present invention to provide a fuel cell device and a method for operating a fuel cell device, where it is possible to easily supply moisture to an anode of the fuel cell.
For the fuel cell device mentioned at the outset, the present invention provides that the anode gas outflow section is connected to the recirculation section in such a way that liquid product water is transferred to the fuel cell. For the method mentioned at the outset, the object is achieved in that water is added to an anode gas conducted to the fuel cell and is removed from the anode exhaust gas of the fuel cell in the form of liquid product water.
Due to these simple measures, it is ensured that the water content of the anode is unable to drop below a predefined setpoint value, since the water missing from the anode may be supplied together with the anode gas. The recirculation section is often used to resupply operating gas still contained in the anode exhaust gas, for example hydrogen, to the fuel cell. To further reduce the effort of wetting the anode, the recirculation section preferably connects the anode gas outflow section to the anode gas inflow section in a water-conducting manner. As a result, the product water may be removed from the fuel cell on the anode side and be supplied to the anode together with the anode gas to be conducted back to the fuel cell. The removed product water may be at least partially added to the anode gas conducted to the fuel cell and be conducted from the anode gas to the anode for the wetting thereof. Due to the fact that the water is supplied to the anode gas in the anode gas inflow section, the fuel cell does not need to be structurally modified.
The approach according to the present invention may be further improved by different embodiments, which are each advantageous per se and, unless otherwise indicated, may be arbitrarily combined with each other. These specific embodiments and the advantages associated therewith are discussed below.
Thus, the anode gas inflow section may be connected to the recirculation section in such a way that water vapor is received therefrom. If the anode has too little moisture, it may be easily wetted by using product water of the fuel cell. The product water is discharged through the anode outflow section during the operation of the fuel cell and may be at least partially used to wet the anode. Adding water from an external source is thus unnecessary. Product water of the fuel cell may thus be added to the anode gas, in particular when it flows through the anode gas inflow section.
The recirculation section may include an anode gas compressor to be able to ensure that a predefined pressure difference drops between an anode gas input and an anode exhaust gas outlet of the fuel cell. Anode exhaust gas is supplied to the anode gas compressor on the inlet side. The anode gas compressor is gas-conductively connected to the anode gas inflow section on the outlet side. Water, in particular product water, is furthermore suppliable to the anode exhaust gas compressor on the inlet side. The product water may be supplied to the anode exhaust gas compressor together with the anode exhaust gas, so that additional lines are not required. The product water is preferably discharged from the fuel cell together with the anode exhaust gas, so that the fuel cell does not have to be structurally modified. The anode gas compressor not only transports the water to the anode gas inflow section, but the water is vaporized before being added to the anode gas conducted to the fuel cell, it being possible to induce the vaporization, in particular, via the anode exhaust gas compressor. Heat, namely, arises during the compression of the anode exhaust gas, with the aid of which the water may be vaporized.
The fuel cell device may include a water separator, through which the anode gas outflow section between the fuel cell and the recirculation section extends. As a result, the product water generated by the fuel cell may be optionally separated or supplied to the anode gas inflow section.
The water separator is preferably designed to specify the quantity of water supplied to the anode gas inflow section. As a result, the quantity of moisture to be supplied to the anode may be set by the water separator. For this purpose, the water separator may include a valve, for example a stop valve or a control valve, through which the product water is optionally conductible away from the fuel cell or to the anode gas inflow section or to the recirculation section.
Particularly during a hot start of the fuel cell, in which the fuel cell is restarted, for example shortly after being taken out of operation, the anode may be efficiently wetted with the aid of the fuel cell device according to the present invention or the method according to the present invention without the complexity of the fuel cell device or the method for operating the fuel cell increasing.